I think I've found the optimal strategy for exploiting Apex. I'm just starting to use it now.

I have found that it's not that hard to make Apex stations appear where none exist. Just create a line of a few dozen fronts. Sooner or later, at least one Apex station will form somewhere in the area. (And if you pick a sufficiently remote area that nobody can find, it will be safe from invasion.)

I have learned that Apex is determined to take over fronts no matter what. When I find an Apex station with no fronts around it, I visit it and build 5 fronts on the perimeter of the circle as close together as possible. Then I build a 6th front as close as possible to the Apex station. Rather than fight Apex for every front, I'm ceding 6 fronts to Apex. Then I'll use an outer ring of fronts to use as my in-game ATM. The inner ring of 6 Apex fronts will give me a steady supply of Apex security officers to mow down so I can upgrade my outer ring of fronts. Relentlessly attacking the Apex sheriff encourages Apex to take over, so that will give me a double benefit - more points for an outer front AND a quicker takeover of the inner fronts.

I thought you can only plant evidence on somebody else's fronts, not your own. Planting evidence is best when you find an area full of many parcels owned by inactive players. (I found just such an area around a small Midwestern city that is full of upgraded parcels, and that's my biggest cash cow at the moment.) However, planting evidence is not an option when you wander off into the remote wilderness where nobody has built any fronts.